1. Field of the Invention
This invention relates to new and useful improvements in bag making machines. More particularly, the present invention relates to bag making machines wherein a heat sealable film is advanced along forming tubes, and is transversely sealed at spaced intervals to form bags. Most particularly, however, the invention is concerned with a bag making machine for the parallel manufacture, especially of tubular bag packings of a low width made from a foil cut into a plurality of strips of identical width, with the strips being continuously and cyclically formed around a corresponding number &tubes and being longitudinally sealed. The term "parallel manufacture" conveys that a corresponding number of tubular bag packings is manufactured simultaneously and in side-by-side relationship around a number of parallel tubes.
2. Description of the Prior Art
Tubular bags of the afore-described type are shown, for example, in German Gebrauchsmuster 93 12 664. Bags of this type have relatively small dimensions, i.e. a width of as little as about 2 cm and a length of about 10 to 15 cm. Bags of this type are manufactured on bag making machines comprising foil advancing elements arranged on an apparatus frame, a strip cutting machine including tubes arranged therebehind in series and in side-by-side relationship and respectively spaced from one another by the interval of a strip width, with the circumference thereof corresponding to the strip width to which are associated--provided that no overlapping sealing is to be effected--guiding elements for narrow internal sealing strips, and elements forming the foil on both sides round the cylindrical tubes, with longitudinal sealing tools being arranged therebehind in the conveying direction and a transverse cutting means being arranged behind the tube ends, coupled to which transverse cutting means is a reciprocating transverse sealing tool. Forming of the cut strips around the tubes is performed in such a way that the abutting edges of each strip are centrally disposed above the introduced internal sealing strips and are longitudinally sealed therewith, whereafter the so formed foil hoses are transversely sealed behind the ends of the tubes, withdrawn by the desired bag length and cut from the following tubular packing foil. Bag making machines of this type, are generally satisfactory in operation. However, problems are involved with preparing the machine, in particular, the special type of bag making machine, for operation and start-up, as the foil is directly introduced into the cutting means. However, the foil is discharged behind the said cutting means in the form of strips cut in parallel. This means that each of the suspending strips, before start-up of the machine, is to be carefully placed manually in abutment with the respective tube to then mount the forming elements and start the actual operation of manufacturing the bags which, incidentally, remain one-sidedly open and unloaded to be subsequently filled and closed in a separate loading and sealing machine. The cutting means hitherto employed on bag making machines of this type are circular cutting knives seated on a spindle and arranged on a cutting table in cooperation therewith, meaning that no permanently sharp severing cuts are insured thereby. However, unsharp cutting edges on the strips are likely to result in butt joints on the bag that are partially permeable to light which would be detrimental for the processing of, for example, light-impermeable packing material.
The afore-described problem is not encountered with a bag making machine according to U.S. Pat. No. 4,079,662 as that machine only operates on one forming tube, apart from the fact that forming of the film around the forming tube is effected by means of a so-called forming shoulder. Such a forming through a forming shoulder is also employed by a packing apparatus according to U.S. Pat. No. 3,354 799, in which several tubular bag packings are simultaneously manufactured in side-by-side relationship. However, for space-saving reasons the forming tubes must be arranged in staggered relationship or at adequately large intervals in order to have available sufficient space for the forming operation through forming shoulders, i.e. four forming tubes respectively require two film bands of corresponding width respectively severed into two strips which are then fed to respectively two forming tubes not arranged in direct adjacent relationship.